1. Field of the Invention
The present invention relates to a chemical heat pump.
2. Description of the Related Art
In recent years, from the standpoint of, for example, efficient use of resources and energy, there has been an increasing need for realization of a “technique of storing heat of an exhaust gas (hereafter referred to as an “inflow gas”) from a factory or the like and using the stored heat to output a gas (hereafter referred to as an “outflow gas”) having a higher temperature than the exhaust gas”. Such a need arises in a case of firing of molded members, for example. In this case, an exhaust gas having been used for cooling high-temperature fired members immediately after firing is used as an “inflow gas” and an “outflow gas” having a higher temperature than the “inflow gas” is output; and the output “outflow gas” is used to increase the temperature of molded members during firing.
As a unit for realizing this technique, a chemical heat pump (a heat pump having a chemically-heat-storing system) has been proposed (for example, refer to Patent Literatures 1 and 2).
The chemical heat pumps described in the literatures have a “reaction section containing a thermal storage medium that undergoes an exothermic reaction and an endothermic reaction”, an “evaporation-condensation section that contains steam and water and causes phase transition between steam and water”, a “connection section connecting the reaction section to the condensation section”, and a “fluid channel that causes heat exchange between a fluid flowing therein and the thermal storage medium”. This “thermal storage medium” has, for example, a property of the thermal storage itself (first property) of that “undergoing an exothermic reaction with steam and forming a hydrate with release of heat”, and a property of the hydrate (second property) of “upon receiving of external heat, undergoing an endothermic reaction for the hydrate and being dehydrated through release of steam from the hydrate and with storing of heat”.
The thermal storage medium has a “transformation temperature”, which is a temperature critical point of state transformation between the thermal storage medium itself (=dehydrated medium) and its hydrate. The transformation temperature of such a thermal storage medium varies depending on the type of thermal storage medium and also fluctuates in response to the ambient pressure of the thermal storage medium. The “exothermic reaction” (dehydrated medium turns into hydrate) in the first property can occur only when the temperature of the inflow gas is equal to or lower than the transformation temperature of the thermal storage medium. The “endothermic reaction” (hydrate turns into dehydrated medium) in the second property can occur only when the temperature of the inflow gas is equal to or higher than the transformation temperature of the thermal storage medium.
In this chemical heat pump, in a heat-storing state, an inflow gas having a temperature higher than the transformation temperature of the thermal storage medium is caused to flow into the fluid channel. When the inflow gas flowing through the fluid channel passes a position where the heat exchange occurs, the hydrate of the thermal storage medium in the reaction section receives heat from the inflow gas. As a result, because of the “second property”, the “endothermic reaction” for the hydrate occurs and the hydrate is dehydrated into the thermal storage medium itself (=dehydrated medium), also causing an increase in the temperature of thermal storage medium (in other words, the thermal storage medium stores heat). The steam (gas) generated by the dehydration moves through the connection section from the reaction section to the evaporation-condensation section. The steam having moved to the evaporation-condensation section undergoes phase transition (condensation) and turns into water (liquid). This water is stored in the evaporation-condensation section. The inflow gas is deprived of heat by the “endothermic reaction”. As a result, the temperature of a gas flowing out from the fluid channel becomes lower than the temperature of the inflow gas flowing into the fluid channel. In summary, in the heat-storing state, an inflow gas having a temperature higher than the transformation temperature of the thermal storage medium is caused to flow into a fluid channel, so that a portion of heat of the inflow gas can be stored in the thermal storage medium (=dehydrated medium).
On the other hand, in a heat-release state, an inflow gas having a temperature lower than the transformation temperature of the thermal storage medium is caused to flow into the fluid channel. Steam generated by phase transition (evaporation) of water in the evaporation-condensation section moves from the evaporation-condensation section to the reaction section. As a result, because of the “first property”, the “exothermic reaction” occurs between the “thermal storage medium (=dehydrated medium) in the reaction section” and “steam”. Thus, the thermal storage medium releases heat and turns into its hydrate. When an inflow gas flowing through the fluid channel passes a position where the heat exchange occurs, the inflow gas receives heat derived from release of heat from the thermal storage medium. As a result, the temperature of an outflow gas flowing out from the fluid channel becomes higher than the temperature of the inflow gas flowing into the fluid channel. In summary, in the heat-release state, an inflow gas having a temperature lower than the transformation temperature of the thermal storage medium is caused to flow into a fluid channel, so that an outflow gas having a higher temperature than the inflow gas can be output.